concurring in the judgment.
Respondent was convicted of several serious offenses in a state trial during which the trial judge learned of a basis for challenging the impartiality of a juror from ex parte, unrecorded conversations with the juror; the judge did not sua sponte inform the parties of the occurrence or the substance of the conversations. Respondent contended, and the courts below held, that he was thereby deprived of liberty without due process of law and entitled to a writ of habeas corpus. Assuming that the respondent was deprived of his right to be present during a critical stage of his trial and his right to *123effective assistance of counsel, the Court vacates on the ground that the state court’s conclusion that the juror was impartial has fair support in the record and hence the constitutional deprivations were harmless beyond a reasonable doubt.
Most of my colleagues “emphatically disagree”1 with the suggestion that a simple test can be used to determine whether an ex parte communication between a trial judge and a juror makes a subsequent jury verdict constitutionally infirm. Nevertheless, I believe both the majority and the dissents gloss over the serious legal issues presented by this case.
The majority concludes that the lower federal courts had a duty to find the alleged constitutional error harmless beyond a doubt because of the state-court conclusion that the jury was impartial. Ante, at 121. Justice Marshall has persuasively shown, however, that there is a reasonable doubt concerning juror Fagan’s impartiality. That doubt forecloses reliance on the harmless error standard enunciated in Chapman v. California, 386 U. S. 18 (1967),2 but that doubt does not require that this petition for a writ of habeas corpus be granted.
In order to evaluate the significance of an alleged constitutional deprivation, it is essential that it first be correctly *124identified.3 The alleged deprivation in this ease has been characterized in three ways: (1) a denial of the defendant’s right to be present at every critical stage of a criminal trial, (2) a denial of the right to effective assistance of counsel at trial, (3) a denial of the right to be tried by an impartial jury.4 *125If respondent had established any of these deprivations, he would have sustained his burden of showing essential unfairness and would be entitled to the issuance of a writ of habeas corpus.
The question whether respondent was deprived of his right to be tried by an impartial jury is not before us, for respondent did not raise this claim in his habeas petition, choosing not to contend that juror Fagan was biased, either as a matter of law or as a matter of fact. 543 F. Supp. 757, 765 (ND Cal. 1982). The majority, however, passes on this question in concluding that the assumed deprivations of the fundamental constitutional rights to counsel and presence at trial were harmless error.
I think it quite clear that the mere occurrence of an ex parte conversation between a trial judge and a juror does not constitute a deprivation of any constitutional right. The defense has no constitutional right to be present at every inter*126action between a judge and a juror, nor is there a constitutional right to have a court reporter transcribe every such communication. The fact that the judge learned of the potential bias of juror Fagan in an ex parte conversation with her is irrelevant in this case. There is no dispute concerning the content of those conversations; if the testimony about the conversations elicited at the post-trial hearing affords a basis for challenging the conviction, it affords a basis for answering those contentions as well. Moreover, to the extent that the claim of partiality is deemed to be before the Court, there is no contention that the post-trial hearing was inadequate to establish the historical facts relevant to assessing whether she was biased as a matter of law. In any event, there is of course no contention that whatever bias she harbored against the Black Panther Party and by inference against the respondent was the result of the conversations with the trial judge, nor is there any basis for suggesting that the conversations exacerbated whatever bias she harbored. Thus, the question in this case would be the same if the judge had learned of the potential bias of juror Fagan from an external source.5
If the trial judge’s actions in this case constitute an error of constitutional dimension, it would have to be on the ground that respondent was denied his core due process right to notice and an opportunity to be heard in a meaningful manner and at a meaningful time by the trial judge’s failure to notify the defense of a fact raising a question about a juror’s partiality. In essence, respondent’s claim is that he had a due process right to a midtrial hearing on the subject of Fagan’s impartiality because of the option which existed at that point of replacing Fagan with an alternate. If such a right exists, the defendant would naturally have a right to be present at *127the hearing and have the assistance of counsel at the hearing, but the existence of this right would not stem from the right to be present or the right to counsel. To argue that the right to counsel and presence is the source of the right to the midtrial hearing is to reason backwards. Naturally since respondent was denied the opportunity for such a hearing, he was denied the incidents of such a hearing, but that does not establish a violation of the incidental rights unless there was a predicate right to notice and a midtrial hearing.
While I believe that the trial judge should have promptly notified defense counsel of the substance of his conversations with juror Fagan, his error was not so fundamental as to render the conviction void. The trial judge made an error of judgment in failing to grasp the fact that Fagan’s previously undisclosed knowledge would provide a basis for challenging her for cause on the grounds of imputed bias. Under the circumstances, that error was understandable, given that the nature of Fagan’s expressed concerns to the judge did not explicitly raise a question of bias against any defendant and only through generalization raised a question of imputed bias against the Black Panther Party — Fagan’s only concern was that she might lose her composure if the murder of her friend were explored in more detail — and that no evidence of respondent’s membership in the Black Panther Party had at that point been introduced. While the good faith of the trial judge is not the question, the reasonableness of his actions under the circumstances is plainly relevant to determining whether they were so fundamentally unfair that they rendered the verdict a nullity. Moreover, respondent was provided with a full and fair opportunity to discover the information about the murder of Fagan’s friend. Three months were devoted to jury selection, and while counsel’s brief, general questions to juror Fagan about her “knowledge” about “crimes [of] violence” as a “witness, victim, [or] otherwise,” and whether she “associated] the Black Panther Party with any form of violence in [her] own mind,” App. C *128to Pet. for Cert. 16, failed to elicit her later revealed knowledge of the murder of her friend, that failure was not a consequence of any shortcoming of the mechanism the State made available for uncovering that information. Finally, the defense ultimately did discover the information, apparently because of the effective assistance of his counsel, and discovered it in time for a meaningful hearing to be held in which the substance of the ex parte conversations and the extent of Fagan’s knowledge of potentially prejudicial information could be established. In light of these factors, I conclude that respondent failed to sustain his burden of demonstrating a deprivation of a right so essential to the integrity of the process by which his conviction was obtained that it renders void the presumptively valid judgment.6
By failing to analyze the real procedural due process question which this case presents, and instead casually assuming the deprivation of the right to counsel and the right to presence — the labels the parties find apt to decribe the essential question — the majority endorses the application of a harmless error analysis to actual deprivations of these rights. Some constitutional rights, however, are so basic to a fair trial that their infraction can never be treated as harmless error. In my opinion the right to the effective assistance of counsel at trial is such a right.7
*129The Court’s reasoning in applying the harmless error analysis must be that the purpose of affording the right to counsel in the circumstances of this case would be to guard against the risk of a biased jury, and hence if the jury was impartial, the risk never materialized and the deprivations were harmless.8 If that reasoning were generally applied, however, *130any deprivation of the right to counsel at trial, perhaps short of totally denying any assistance whatsoever, could be deemed harmless error. Fidelity to the Sixth Amendment and to precedent demands that such reasoning be rejected.
Finally, the majority concludes that Fagan’s presence on the jury did not prejudice respondent, casually attaching the “beyond a reasonable doubt” label to the conclusion made obligatory by the presumed constitutional violations. I find it extraordinary that the majority is prepared to hold in essence that juror Fagan was impartial beyond a reasonable doubt.9 The undisputed facts concerning the murder of her friend may not have rendered her biased as a matter of law— *131a question which we need not decide — but they surely establish a reasonable doubt concerning her impartiality, and the presumptively correct findings of the state courts that she was not biased as a matter of fact erase neither the doubt nor the reasonableness of it.
In summary, although I agree that respondent has not carried his burden of establishing that his trial was fundamentally unfair, I cannot subscribe to the Court’s assumption that a violation of the right to the assistance of counsel at trial, if established by the record, could be characterized as harmless beyond a reasonable doubt. Nor can I subscribe to the Court’s analysis of the harmless error conundrum of its own making. I therefore concur in the judgment but do not join the Court’s opinion.
Compare:
“The Court of Appeals for the Ninth Circuit affirmed on the basis that an unrecorded ex parte communication between trial judge and juror can never be harmless error.
“We emphatically disagree.” Ante, at 117 (footnote omitted), with:
“To the extent that the majority means to imply that judges and jurors may freely engage in ex parte discussions of ‘aspect[s] of the trial,’ I emphatically disagree.” Post, at 139, n. 19.
As the Court has often stated, “before a federal constitutional error can be held harmless, the court must be able to declare a belief that it was harmless beyond a reasonable doubt.” Chapman v. California, 386 U. S., at 24.
As I have previously explained, claims of constitutional error are not fungible.
“There are at least four types. The most frequently encountered is a claim that attaches a constitutional label to a set of facts that does not disclose a violation of any constitutional right.. . . The second class includes constitutional violations that are not of sufficient import in a particular case to justify reversal even on direct appeal, when the evidence is still fresh and a fair retrial could be promptly conducted. Chapman v. California, 386 U. S. 18, 22; Harrington v. California, 395 U. S. 250, 254. A third category includes errors that are important enough to require reversal on direct appeal but do not reveal the kind of fundamental unfairness to the accused that will support a collateral attack on a final judgment. See, e. g., Stone v. Powell, 428 U. S. 465. The fourth category includes those errors that are so fundamental that they infect the validity of the underlying judgment itself, or the integrity of the process by which that judgment was obtained.” Rose v. Lundy, 455 U. S. 509, 543-544 (1982) (Stevens, J., dissenting).
In order to obtain habeas corpus relief from incarceration pursuant to a presumptively valid state-court judgment, a prisoner must persuade a federal court that the most serious kind of constitutional error infected the proceedings that led to his conviction. “It is of the historical essence of habeas corpus that it lies to test proceedings so fundamentally lawless that imprisonment pursuant to them is not merely erroneous but void.” Fay v. Noia, 372 U. S. 391, 423 (1963). Moreover, “the burden of showing essential unfairness [must] be sustained by him who claims such injustice and seeks to have the result set aside, and ... it must be sustained not as a matter of speculation but as a demonstrable reality.” Adams v. United States ex rel. McCann, 317 U. S. 269, 281 (1942).
The California Court of Appeal, the first court to confront respondent’s claim that he had been deprived of liberty without due proces of law, stated that the issue before it arose “at the confluence of three streams of constitutional doctrine, flowing from the right of defendants in criminal proceedings to trial by an impartial jury, their right to be personally present during the proceedings, and their right to be represented by an attorney.” App. C to Pet. for Cert. 22-23. Instead of analyzing the serious questions the case presents, however, the court merely assumed that “there was fed*125eral constitutional error committed as a consequence of the in camera conversations between Fagan and the trial judge in that neither [respondent] nor [his] counsel were present.” Id., at 23. The court then proceeded to determine whether this ill-defined “constitutional error” was harmless beyond a reasonable doubt. In doing so, the court essentially ignored the constitutional deprivation it had assumed, and instead concluded that Fagan’s recollection of her friend’s murder at the hands of a Black Panther did not deprive respondent of his right to an impartial jury. The only role played by the “constitutional error” in the court’s analysis was that it allocated the burden of proof to the State to show “beyond a reasonable doubt” that the jury was not biased. The California Court of Appeal’s unfortunate mode of analyzing this ease is regrettably repeated in this Court.
I understand that the Court’s approach to this case is largely a function of petitioners’ apparent concession below that the ex parte communications established a constitutional violation. An apparent concession is all that it is, however, for petitioners’ concession is so amorphous as to be meaningless and the parties actually argue the substance of the constitutional questions under the harmless error label. Indeed, the District Court recognized the illusory nature of petitioners’ concession: it refused to assume the existence of a constitutional deprivation without substance or content and proceeded to determine for itself whether the facts disclosed violations of constitutionally secured rights. 543 F. Supp. 757, 765 (ND Cal. 1982).
Indeed, the case would not be very different if defense counsel had learned of the potential bias in the course of the trial, and the trial judge denied a motion for a midtrial hearing on the question, but held a post-trial hearing.
If respondent had a fundamental due process right to notice of the substance of the communication between the judge and the juror and an opportunity for a hearing on the matter during midtrial, the reason for recogniz-ipg such a right would stem from the fact that juror bias questions are inherently speculative and that the meaningful time for a hearing on such questions is at a point in time when doubts about impartiality can be easily remedied by replacing the juror with an alternate. A deprivation of a right with such a rationale could not be held to be harmless error. See, e. g., Chapman v. California, 386 U. S. 18, 52, n. 7 (1967) (“[PJartic-ular types of error have an effect which is so devastating or inherently indeterminate that as a matter of law they cannot reasonably be found harmless”) (Harlan, J., dissenting). This, in substance, is what the lower courts held.
Chapman v. California, 386 U. S., at 23, and n. 8; id., at 42-44 (Stewart, J., concurring in result): id., at 52, and n. 7 (Harlan, J., dissenting); *129see Gideon v. Wainwright, 372 U. S. 335 (1963); Glasser v. United States, 315 U. S. 60, 76 (1942) (“The right to have the assistance of counsel is too fundamental and absolute to allow courts to indulge in nice calculations as to the amount of prejudice arising from its denial”); Johnson v. Zerbst, 304 U. S. 458 (1938); Powell v. Alabama, 287 U. S. 45 (1932); see also Cuyler v. Sullivan, 446 U. S. 335, 349-350 (1980); Geders v. United States, 425 U. S. 80 (1976); Herring v. New York, 422 U. S. 853, 863 (1975). The Court has permitted harmless error analysis regarding deprivations of the right to counsel at pretrial stages of criminal proceedings, e. g., Coleman v. Alabama, 399 U. S. 1 (1970), but see White v. Maryland, 373 U. S. 59 (1963) (per curiam), and naturally permits such analysis when the violation of the Sixth Amendment consists of the admission of evidence, since it is ordinarily possible to ascertain whether consideration of inadmissible evidence is harmless error, compare United States v. Henry, 447 U. S. 264, 274-275, n. 13 (1980), with Massiah v. United States, 377 U. S. 201 (1964); see also Moore v. Illinois, 434 U. S. 220 (1977).
In United States v. Morrison, 449 U. S. 361 (1981), we assumed that a pretrial unsuccessful attempt by Government agents to deprive a defendant of her right to effective assistance of counsel was a violation of the Sixth Amendment and held that dismissal of an indictment is not a proper remedy for that assumed violation. Morrison is not a harmless error case. The opinion did observe that even if the Government agents had managed to elicit incriminating information from the defendant, in violation of Massiah v. United States, supra, in their otherwise unsuccessful attempt to persuade her to cooperate and to discharge her attorney, her remedy for that violation would simply be to suppress the tainted evidence. The erroneous admission of such evidence would be susceptible to a harmless error analysis, as the opinion indicated when it then noted in passing that “certain” violations of the right to counsel may be disregarded as harmless error, correctly citing Moore v. Illinois, supra, as identifying the types of violations which may be treated as harmless error — a limited exception to our conclusion in Chapman. 449 U. S., at 365.
Whether application of this analysis is appropriate with respect to the purported right-to-presence violation is largely a question of semantics. The right to be present at trial is rooted in the Confrontation Clause. Illinois v. Allen, 397 U. S. 337, 338 (1970). If a defendant were denied ac*130cess to the courtroom while the prosecutor was examining his accusers, the constitutional error would taint the verdict no matter how firmly we might be convinced that the defendant’s absence did not affect the outcome of the trial. See Snyder v. Massachusetts, 291 U. S. 97, 116 (1934) (“[Cjonstitu-tional privileges or immunities may be conferred so explicitly as to leave no room for an inquiry whether prejudice to a defendant has been wrought through their denial”). Even so, a very brief absence might be held to be a de minimis violation and afford no basis for relief. Ibid. Moreover, we have viewed a potential for prejudice as a necessary element of a violation of the right to be present. Thus, while a core Confrontation Clause violation might not be deemed harmless error, the more general right to presence may be inherently susceptible to a harmless error analysis. Id., at 114-118.
The majority uses the phrase the jury’s deliberations “as a whole” were not biased. Ante, at 120, 121. Unless one can say beyond a reasonable doubt that juror Fagan’s deliberations were not improperly influenced by her knowledge of the murder of her friend at the hands of a Black Panther, I fail to see how one can conclude that the jury’s deliberations “as a whole” were not biased. Hence, I fail to see the point in not focusing on Fagan in this analysis. Respondent has never made any serious effort at establishing that the other jurors’ knowledge of the murder of Fagan’s friend directly influenced their thoughts about the case. I cannot believe that the majority means to imply that an additional showing of prejudice is required after one of the jurors is established to be prejudiced. Surely, a defendant has a right to impartiality on the part of all of the jurors, and a violation of that right is plainly not susceptible to a harmless error analysis. See Tumey v. Ohio, 273 U. S. 510 (1927).